Wide frequency range current-controlled oscillator

A current-controlled oscillator for providing a digital output signal that has a frequency controllable by an input control current and that has substantially a fifty percent duty cycle, said current-controlled oscillator comprising:

• a timing-capacitor for storing a timing-capacitor voltage;
• a first current mirror coupled to the timing capacitor and the input control current for providing a current having a magnitude substantially the same as the magnitude of the input control current;
• a differential voltage comparator having first and second inputs, the second input coupled to the junction of the timing capacitor and the first current mirror for comparing the timing-capacitor voltage with the voltage at the differential-comparator first input and providing an output signal when the magnitude of the timing-capacitor voltage is greater than the magnitude of the voltage at the differential-comparator first input;
• a first switchable current mirror coupled to the junction of the timing-capacitor and the first current mirror for sinking when enabled a current having a magnitude that is substantially twice the magnitude of the input control current;
• and
• a switchable reference voltage circuit having first and second reference voltages, the first reference voltage greater than the second reference voltage, said switchable reference voltage circuit coupling the first reference voltage to the differential-comparator first input, disabling the first switchable current mirror to charge the timing capacitor and providing a predetermined second state of the digital output signal when the differential-comparator output signal is not present;
• and coupling the second reference voltage to the differential-comparator first input, enabling the first switchable current mirror to discharge the timing capacitor and providing a predetermined first state of the digital output signal when the differential-comparator output signal is present.

A current-controlled oscillator for providing an oscillator signal that is frequency controllable by an input control current, said current-controlled oscillator comprising:

• timing-capacitor means for storing a timing-capacitor voltage;
• current source means coupled to the timing capacitor means and the input control current for providing a first current having a predetermined magnitude dependent on the magnitude of the input control current;
• switchable current mirror means coupled to the junction of the timing-capacitor means and the current source means for sinking when enabled, a second current having a magnitude that is related to the magnitude of the first current by a predetermined factor greater than one;
• and
• differential voltage comparator means having first and second reference voltages, where the first reference voltage is greater than the second reference voltage, the differential voltage comparator means coupled to the junction of the timing-capacitor means and the current source means for comparing the timing capacator voltage with the first and second reference voltages, the differential comparator means enabling the switchable current mirror means when the magnitude of the timing-capacitor voltage is substantially the same as the magnitude of the first reference voltage and subsequently disabling the switchable current mirror means when the magnitude of the timing-capacitor voltage is substantially the same as the magnitude of the second reference voltage.